Centrifuge apparatus



5 E. G. PICKELS 3,350,002

CENTRIFUGE APPARATUS Filed March 14. 1963 JNV EN -17 EDWARD G. PIC S H WQWMW ATTORNEYS United States Patent 3,350,002 CENTRIFUGE APPARATUS Edward G. Pickels, Atherton, Califi, assignor to Beckman Instruments, Inc., a corporation of California Filed Mar. 14, 1963, Ser. No. 265,089 17 Claims. (Cl. 233-28) This invention relates generally to centrifuge apparatus and more particularly to a rotor for such apparatus.

In prior continuous flow centrifuge apparatus, a rotor assembly is provided wherein sediment deposited by centrifugation is readily resuspended for further treatment or analysis. One rotor assembly includes a cylindrical core enclosed in a surrounding shell or bowl. For centrifugation operations the core is maintained concentrically fixed with respect to the bowl. An annular space is thereby defined between the core and the bowl to form a separating chamber having surfaces wherein deposited sediment accumulates. The accumulated sediment is resuspended after centrifugation.

A releasable axial sleeve is first removed so that the core is no longer held axially fixed with respect to the shell. The rotor is then filled with a suitable resuspension liquid, such as distilled water, plugged, and laid on its side. With its axis disposed horizontally, the rotor is rotated by suitable means. During this rotation, the core ri-des freely on the inner wall of the bowl to agitate the sediment whereby the latter is resuspended in the liquid.

It is a general object of the present invention to provide an improved rotor suitable for continuous flow centrifugation.

Another object of the invention is to provide a core means which is contractable under radially inwardly acting centripetal forces which are generated during centrifugation so that contraction of the core serves to form a separation chamber defined between the inner wall of the bowl and the outer periphery of the core means.

Another object of the invention is to provide arotor assembly wherein the core is freed and expands after centrifugation whereby it can ride freely on the inner wall of the bowl during resuspension of deposited sediment.

It is a more specific object of the invention to provide a-rotor assembly wherein during centrifugation the core is urged radially inwardly by centripetal forces to contract the perimeter of same and form a separation chamber and wherein Withdrawal of these forces frees the core so that it can move into contact with the inner wall of the bowl during subsequent sediment-resuspension operations.

Still another object of the invention is to provide a rotor assembly having a free, segmented core wherein the segments have a predetermined specific gravity selected to cause the segments to move toward the axis of the rotor during centrifugation.

Another object of the invention is to provide a centrifuge rotor having a low hold-up volume.

These and other objects, features and advantages of the invention will be more readily apparent from the following detailed description of a preferred embodiment of the invention when taken in conjunction with the drawings in which:

FIGURE 1 shows a centrifuge rotor apparatus, in section, disposed for operation in a continuous flow centrifuge. For example, see United States Patent No.

3,073,517, granted Jan. 15, 1963, assigned to the assignee herein.

FIGURE 2 is a section of FIGURE 1 taken along the line 2-2 thereof and proportionately reduced.

FIGURE 3 is a diagrammatic perspective view showing a segment of the core shown in FIGURE 1.

FIGURE 4 shows another embodiment of a core segment.

In general, there is provided a centrifuge rotor assembly for both batch and continuous centrifugation of liquid sample and resuspension of sediment recovered from the centrifugation. The rotor assembly comprises a hollow bowl formed with an upwardly extending inner wall, and contains a core means mounted to be rotated with the bowl about a generally vertical axis. The perimeter of the core means contracts under urging of radially inwardly acting centripetal forces generated during centrifugation. This contraction of the core provides a separation chamber defined between the inner wall of the bowl and the outer periphery of the core means. Termination of centrifugation removes these forces from the core means to free it for movement into contact with the inner wall of the bowl. Resuspending the deposited sediment may then proceed immediately as the next step. The rotor assembly may further include fluid passage means forming a path for passing liquid sample continuously into and out of the separation chamber during centrifugation.

Centrifuge apparatus is shown in FIGURE 1. The parts in phantom lines represent parts as generally disclosed in my patent, referred to above. Portions of this structure are described further below.

In FIGURE 1 a rotor assembly 10 includes means forming a hollow bowl 11. Bowl 11 is formed with an upwardly extending inner Wall 12 which curves radially inwardly at both ends to form openings 13 and 14, respectively. The surface of wall 12 merges with the surface of openings 13 and 14.

Means are provided for mounting bowl 11 for rotation about its vertical axis during centrifugation. The mounting means may include an annular cap 17 formed with coaxially arranged threaded recesses 18 and 19. Threads of recess 18 engage threads on the exterior of portion 16. Bowl 11 can be locked with respect to cap 17 by suitable means such as the transverse pin 20 disposed in a hole 21 drilled through the side wall of the cap 17 and into portion 16. Pin 20 can be secured in place either by a plug or by threads formed on its outer end.

In order to connect cap 17 for rotation with a rotor mounting element such as a stub shaft (not shown) there is provided a pair of downwardly projecting pins 22 adapted to be received in co-acting holes formed in such a mounting element. Pins 22 are located inside an axially depending sleeve 23 adapted to fit over the mounting element (not shown).

In continuous centrifugation, liquid sample can be supplied from a reservoir into a fluid feed or receiving chamber located near the axis of rotation. The liquid then passes radially outwardly to a separation chamber between the core and bowl. The outer wall of the separation chamber collects the sediment, and the remaining liquid then passes to a fluid removal chamber. The latter discharges to a suitable receiving vessel.

As disclosed herein, many of these functions are performed by a core assembly 30 within bowl 11 as now to be described.

Means forming part of core assembly 30 are provided for introducing fluid sample axially into the rotor assembly 10 from a supply vessel (not shown). Accordingly, a hollow center post 31 is disposed co-axially of bowl 11. The interior of center post 31 forms a fluid feed chamber 32. Chamber 32 is open at the upper end to receive fluid sample therein as supplied, for example, via a downwardly depending tubular shaped member 44.

Fluid passage means forming a path for passing liquid sample out of chamber 32 is formed by transverse openings 34 disposed near the bottom of chamber 32. Means are further provided whereby center post 31 is readily removable from bowl 11. The bottom of post 31 is threadedly engaged in recess 19 and locked with respect to cap 17 by suitable means such as the transversely extending pin 35.

In general, core assembly further includes a generally cylindrically-shaped, segmented core body 33 which loosely encircles center post 31. Core body 33 is made up of a plurality of segments 36 such as shown in FIG- URE 3 which are individually and collectively responsive to application of centripetal forces generated during centrifugation of liquid sample. These forces urge the segments toward the axis of the rotor. Thus, the perimeter of the core body contracts to form a separation chamber 37 of flow hold-up volumn. Chamber 37 accumulates sediment on its outer wall 12 during centrifugation. Chamber 37 is thus defined by the wall 12 and the peripheral surface of core body 33.

More specifically, it will be noted that segments 36- of core body 33 are arranged in tiers stacked to rest loosely one upon the other. The tiers are defined between spaced planes 38 disposed transversely to the axis of rotor assembly 10. Core body 33 is further separated, as shown in FIGURE 2, to provide a transverse cross section defining an annulus 39 separated into a plurality of generally pie-shaped portions. While the foregoing rather extensive segmental subdividing of the core body is preferred, it is to be understood from the operation as explained furtherbelow that the core body can be merely divided into vertically elongated segments formed only with the pieshaped cross section without separating same into tiers. Furthermore, it may be desirable to use some complete tiers together with some which are divided by radial separations. Where complete tiers are desired the bowl 11 can be made in two parts permitting each annulus to be inserted.

Segments 36 are made from suitable material, such as plastic, wherein the overall specific gravity of the segment is relatively low. Accordingly, they can be either solid or hollow. For effective operation the specific gravity of segments 36 should be less than the constituents of the liquid sample being centrifuged. Under these conditions segments 36 will float toward the axis of rotation, that is, they will be forced against center post 31 during centrifugation. As one example, using a liquid sample with a specific gravity of 1.3, the segments will float inwardly when prepared to have a specific gravity of 1.2. In this manner, under high speed rotation, separating chamber 37 is formed as shown in FIGURE 1.

Means are provided at the upper end of bowl 11 to form a fluid removal chamber 24. One suitable arrangement can include a cup-shaped cap member 25 formed with an axial recess 26 and a co-axial opening 27 at the upper end thereof. A threaded portion 28 extends around the lower edge of recess 26 to engage threads formed around the exterior of portion 15. A locking pin 29 extends into a transverse registration hole formed to extend into the threaded portion of bowl 11. Fluid removal chamber 24 therefore has a smooth side wall continuous from wall 12 and opening 13 to facilitate removal of fluid from the rotor assembly.

The means shown in phantom lines serves to pump fluid sample from fluid removal chamber 24 in the manner described herein further below.

As noted above the wall of opening 13 merges with the surface of wall 12. The exterior surface 40 of center post 31 extends into opening 13 to form a fluid passage 41 leading out of separating chamber 37 and into fluid removal chamber 24.

From the foregoing it will be evident that the rotor assembly 10 is very simple to assemble. Cap 17 is screwed onto portion 16 of bowl 11 and locked in place by inserting pin 20. Segments 36 are then dropped into bowl 11 and arranged in annular tiers as shown. Center post 31 is then fished axially down through bowl 11 and screwed into recess 19. Pin is inserted to lock center post 31 with respect to bowl 11. Then, with the pump unit of the centrifuge in position (as shown in phantom lines), cap 25 is screwed onto the top of bowl 11 and locked in place by pin 29.

Operation of the above rotor assembly is as follows. During centrifugation a sample to be separated is fed from a supply vessel (not shown) via tubular member 44 and into fluid feed chamber 32. The fluid rides gently onto the vertical wall of chamber 32 under the influence of centrifugal force. Fluid feeds outwardly via passages 34 into the lower end of separating chamber 37. Fluid progresses upwardly in separating chamber 37, then inwardly, and again upwardly in passage 41 finally entering removal chamber 24. While the fluid is in separating chamber 37, sediment is deposited due to high centrifugal forces encountered.

Fluid in removal chamber 24 is removed by any suitable means. For example, the structure shown in the above-identified application includes a pump comprising merely a pair of spaced discs 45, 46. The pump operates in the following manner: when the rotor is operated at relatively high velocity, liquid sample within the rotor is urged outwardly by centrifugal force. The liquid rides against the outer wall of chamber 24 and forms a vertical wall of fluid, illustrated at 42 in FIGURE 1. The rotational velocity of the fluid between the plates 45, 46 is reduced by frictional engagement with the plates. Consequently, the centrifugal force and accompanying pressure is reduced in this area. The higher pressure exerted by the remainder of the fluid in chamber 24, which fluid is at full rotor rotational velocity, forces the sample inwardly between plates 45, 46 and through an annular axial opening 47 formed in the vertically disposed tubular member 44.

Chamber 24 is continuously replenished with liquid sample a follows. As sample is fed into fluid feed chamber 32, the vertical wall of fluid therein will have a smaller diameter than the wall 42 of fluid in removal chamber 24. As a result there will be a pressure difference which causes the fluid to flow continuously through the rotor. This difference in head is present because of frictional drag through passages 34, 41 and separating chamber 37. The incoming fluid entering chamber 32 displaces the resident fluid in the rotor in a direction toward removal chamber 24.

During centrifugation, heavy particles are acted upon by centrifugal force and settle out packed again-st wall 12. To recover the deposited sediment various procedures can be followed.

One method as explained above which has previously been followed is to remove a supporting part of the assembly which holds the core assembly fixed within the bowl. The core assembly can then ride freely upon the inner wall of the bowl when laid on its side. A fluid suitable for mixing with the sediment is introduced into the rotor and the rotor sealed by a plug. By placing the rotor on its side and rotating it, the core agitates the sediment from the inner wall of the bowl to resuspend it in the mixing fluid. As explained in the above-identified application the liquid in front of the core is pushed ahead of the rolling core. The core may also slip somewhat to give rise to a scraping action.

In the present apparatus the rotor assembly is automatically ready to resuspend sediment as soon as centrifugation has terminated.

If the above outlined procedure is followed, the rotor is removed from the centrifuge. A suitable mixing fluid is then poured into the rotor via opening 27 and a cork inserted. The rotor assembly can then be laid on its side and rotated, as by resting the same on rollers.

During rotation segments 36 are free to move into contact with inner wall 12 of bowl 11 so as to agitate the sediment. If desired, center post 31 can be unscrewed from recess 19 and left substantially in place so as to apply additional agitating weight to segments 36. In this manner, the center post provides a readily releasable means for applying additional compressive force between core body 33 and wall 12 when the rotor is conditioned horizontally for resuspension operation.

On the other hand, if suitable rollers are not readily available, the sediment can be resuspended merely by agitating center post 31 by hand in the presence of a suitable mixing liquid. Thus, segments 36 can be moved outwardly into scraping contact with wall 12. To enhance the scraping action, according to another embodirnent'of the invention, outwardly projecting scraping members 43 as shown in FIGURE 4 can be formed on the surfaces 44 of segments 36.

From the foregoing it will be evident that there has been provided a simplified centrifuge rotor apparatus wherein the core means is responsive to centripetal forces generated during centrifugation of liquid sample. Under these centripetal forces the segments float toward the axis of rotation so as to contract the perimeter of the core means. Subsequently, however, the core means is free upon withdrawal of these forces to move into contact with the inner wall of the bowl so as to aid in resuspending deposited sediment. It should also be noted that the hold-up volume, i.e. the volume between the fluid feed chamber and the fluid removal chamber is minimized.

I claim:

1. A centrifuge rotor assembly for centrifugation of liquid sample and resuspension of sediment recovered therefrom comprising a hollow bowl formed with an upwardly extending inner wall, a core body carried within said bowl and disposed about a vertical axis for centrifugation operations, said core body having a substantially cylindrical outer surface and being free to rotate independent of said hollow bowl, said core body comprising discrete segments contractable during centrifugation to provide a separation chamber for accumulating sediment, said separation chamber being defined by said inner wall of said bowl and said outer surface of said core body, and said core body being free upon termination of centrifugation to move toward said inner wall of said bowl and ride along said inner wall to remove said sediment therefrom for resuspending said sedment.

2. A centrifuge rotor assembly as defind in claim 1 further including fluid passage means for conducting liquid sample continuously into and out of said separation chamber during centrifugation.

3. A centrifuge rotor assembly for centrifugation of liquid sample and resuspension of sediment recovered therefrom comprising a hollow bowl formed with an upwardly extending inner wall, a core assembly including a core body carried within said bowl and disposed about a vertical axis for centrifugation operations, said core body being free to rotate independent of said hollow bowl, comprising discrete segments, and having a substantially cylindrical outer surface, said core body being subject to centripetal forces generated during centrifugation and acting radially inwardly to contract said outer surface of said core body to provide a separation chamber for accumulating said sediment, said chamber being defined by said inner wall of said bowl and said outer surface of said core body, and said core body being free upon withdrawal of said forces to move toward said inner wall of said bowl and ride along said inner wall in scraping contact to remove said sediment therefrom for resuspending said sediment.

4. A centrifuge rotor assembly as defined in claim 3 further including fluid passage means for conducting liquid sample continuously into and out of said separation chamber during centrifugation.

5. Centrifuge apparatus as defined in claim 3 wherein said core assembly further includes releasable means disposed in said core body for applying additional compressive force between said core body and said inner wall during said resuspension operation.

6. Centrifuge apparatus as defined in claim 5 wherein said releasable means includes a hollow center post disposed coaxially of said bowl, said post being open at one end to form a fluid feed chamber for receiving liquid sample, and a fluid passage for conducting liquid sample to said separating chamber from said fluid feed chamber.

7. Centrifuge apparatus as defined in claim 6 wherein said center post is removable from said bowl.

8. Centrifuge apparatus as defined in claim 5 wherein said bowl includes a cylindrical opening at one end, the wall of said opening merging with the inner wall of said bowl, and wherein said releasable means includes a center post disposed coaxially of said bowl and extending into said opening to form a fluid passage leading out of said separating chamber, said passage being defined between the exterior of said center post and said wall of said cylindrical opening, said center post being hollow to form a fluid feed chamber and open at one end to receive liquid sample, and a fluid passage interconnecting said fluid feed chamber and said separating chamber.

9. In centrifuge apparatus, a rotor assembly for centrifugation of liquid sample and resuspension of sediment recovered therefrom, said rotor assembly comprising a hollow bowl formed with an upwardly extending inner wall, core means having an outer surface and being contractable under radially inwardly-acting centripetal forces generated during centrifugation thereby forming a separation chamber, said separation chamber being defined between said inner wall of said bowl and said outer surface of said core means, and said core means expanding to ride along said inner wall of said bowl in scraping contact to scrape said sediment therefrom when said centripetal forces decrease after centrifugation.

10. Centrifuge apparatus as defined in claim 9 further including fluid passage means for conducting liquid sample continuously into and out of said separation chamber during centrifugation.

11. A centrifuge rotor assembly for centrifugation of liquid samples and resuspension of sediment recovered therefrom comprising a hollow bowl formed with an upwardly extending inner wall, a core assembly including a core body carried within said bowl and mounted to be rotated therewith about a vertical axis for centrifugation operation, said core body formed from a plurality of discrete, loose segments carried within said bowl and having a substantially cylindrical outer surface, said core body being subject to centrifugal forces generated during centrifugation and acting radially inwardly to contract said outer surface of said core body to provide a separation chamber for accumulating said sediment, said chamber being defined by said inner wall of said bowl and said outer surface of said core body, and said core body being free upon withdrawal of said forces to move into contact with said inner wall of said bowl for resuspending said sediment, whereby during centrifugation said segments move away from said wall and during resuspension operations said segments move into contact with said wall.

12. Centrifuge apparatus as defined in claim 11 wherein said core body segments are movable radially f0 and from said inner wall of said bowl, said segments having a predetermined specific gravity.

13. Centrifuge apparatus as defined in claim 11 wherein said core body is separated into a plurality of segments arranged in tiers stacked to rest loosely one upon the other.

14. Centrifuge apparatus as defined in claim 11 wherein said core body has a transverse cross section defining an annulus separated into a plurality of segments, each segment forming a generally pie-shaped portion of the annulus.

15. A centrifuge apparatus as defined in claim 11 wherein said core body is separated into a plurality of segments arranged in tiers stacked to rest loosely one upon the other, said core body having a transverse cross-section'defining an annulus, each segment forming a generally pie-shaped portion of said annulus.

16. Centrifuge apparatus as defined in claim 11 where in said segments are provided with scraping elements disposed to coact with said inner wall of said bowl.

17. Centrifuge apparatus defined in claim 12 where- 2,712,896 7/ 1955 Bo1din 23328 in the specific gravity of said segments is less than said 3,145,173 8/1964 Sharples 233-20 liquid sample- FOREIGN PATENTS References Cited 5 1,246,757 10/1960 France.

UNITED STATES PATENTS M. CARY NELSON, Primary Examiner.

2,209,043 7/1940 Strezynski 233-27 H. KLINKSIEK, Assistant Examiner.

2,661,150 12 /1953 Abbott 233-27 

1. A CENTRIFUGAL ROTOR ASSEMBLY FOR CENTRIFUGATION OF LIQUID SAMPLE AND RESUSPENSION OF SEDIMENT RECOVERED THEREFROM COMPRISING A HOLLOW BOWL FORMED WITH AN UPWARDLY EXTENDING INNER WALL, A CORE BODY CARRIED WITHIN SAID BOWL AND DISPOSED ABOUT A VERTICAL AXIS FOR CENTRIFUGATION OPERATIONS, SAID CORE BODY HAVING A SUBSTANTIALLY CYLINDRICAL OUTER SURFACE AND BEING FREE TO ROTATE INDEPENDENT OF SAID HOLLOW BOWL, SAID CORE BODY COMPRISING DISCRETE SEGMENTS CONTRACTABLE DURING CENTRIFUGATION TO PROVIDE A SEPARATION CHAMBER FOR ACCUMULATING SEDIMENT, SAID SEPARATION CHAMBER BEING DEFINED BY SAID INNER WALL OF SAID BOWL AND SAID OUTER SURFACE OF SAID CORE BODY, AND SAID CORE BODY BEING FREE UPON TERMINATION OF CENTRIFUGATION TO MOVE TOWARD SAID INNER WALL OF SAID BOWL AND RIDE ALONG SAID INNER WALL TO REMOVE SAID SEDIMENT THEREFROM FOR RESUSPENDING SAID SEDMENT. 